The primary aim of the present study was to examine the haemodynamic changes in primary hypertension and secondary hypertension (renal diseases, endocrine diseases, obesity-associated hypertension) with a non-invasive haemodynamic measurement protocol utilizing radial pulse wave analysis and whole-body impedance cardiography in both supine position and during head-up tilt. For comparison, haemodynamics of subjects with chronic fatigue syndrome will also be recorded.